Conventionally, as a blur correction apparatus, there is an known apparatus which corrects a camera shake by moving a movable part holding a lens or an imaging element (optical member) of a camera along a plane perpendicular to an optical axis in relation to a fixed part.
This type of blur correction apparatus generally comprises a plurality of balls as a spacer which is arranged between a movable part and a fixed part, a plurality of coil springs which draw and tension the movable part toward the fixed part so as to sandwich the plurality of balls in the optical axis direction, and two sets of voice coil motors (VCMs) which move the movable part in the plane direction in relation to the fixed part.
The VCM ordinarily comprises a magnet provided on one of the movable part and the fixed part, a coil provided on the other one of the movable part and the fixed part, and at least one yoke which forms a magnetic circuit in combination with the magnet and the coil. The yoke is provided on at least one of the movable part and the fixed part.
Another retention mechanism is also known which uses a magnetic spring to attract and hold the movable part to the fixed part, in place of providing a plurality of coil springs. As an example of the magnetic spring, there is a known configuration in which a movable part is attracted to a fixed part by using a magnetic attraction force between a magnet provided on the movable part (or fixed part) and a yoke provided on the fixed part (or movable part), to hold the movable part between both parts (for example, Jpn. Pat. Appln. KOKAI Publicaiton No. 2013-88684). That is, when such a magnetic spring is used, no coil spring is required and the apparatus configuration can be simplified accordingly.
However, in an apparatus using this type of magnetic spring, there is a difficulty in obtaining appropriate magnetic attraction force of magnification for holding a movable part at a fixed part without spoiling an original function (i.e., the function to improve output of the VCM). It is therefore difficult to simultaneously perform both functions satisfactorily.
Since the yoke ordinarily has a size substantially equal to a magnet, the magnetic attraction force which is generated in combination with the magnet is greater, compared with the attractive force of a coil spring when this kind of magnetic spring is used. Therefore, the force with which a plurality of balls are sandwiched in an optical axis direction becomes excessive, and the movable part and fixed part tend to be easily worn out and degraded due to sliding contact with the balls.
Also, when this type of magnetic spring is used, a magnet or a yoke needs to be provided on the movable part. In any case, the movable part is heavy, and power consumption of the VCM therefore increases.
The present invention has been made in view of circumstances as described above and has an object of providing a retention mechanism capable of attracting a movable part toward a fixed part with appropriate force, a driving apparatus capable of efficient stable operation without an increase in weight of the movable part, and a blur correction apparatus using the retention mechanism and/or the driving apparatus.